Now, in addition to the islands, health authorities are preparing for the virus to infect people in the U.S. itself.

“It’s not a matter of if, but when,” Dr. James Crowe, an infectious disease expert at Vanderbilt University, recently said to USA Today.

According to the National Association of County and City Health Officials (NACCHO), “it is virtually certain” that the virus will become established in the U.S. According to Paul Etkind, senior director for infectious diseases at NACCHO, “Local health departments should expect to see more of these cases as travel to the Caribbean for business and pleasure purposes increases over time. In addition, hundreds of thousands of soccer fans, many from the United States, are expected to travel to Brazil in July for the World Cup. The opportunities for introduction of the virus via infected fans returning from the games will be many.”

So far, all of the confirmed and suspected cases have involved people who have traveled to the Caribbean recently. However, there is potential for the virus to take hold here in the U.S. — just like West Nile virus did more than a decade ago.

Chikungunya is spread by the yellowfever mosquito (Aedes aegypti) and by the Asian tiger mosquito (Aedes albopictus), both of which are present in North America. If one of these mosquitoes bites an infected person, it then has the potential to spread the virus by biting others.

The most common symptoms of chikungunya are fever and joint pain. Other symptoms may include headache, muscle pain, joint swelling, or rash. However, it is very rarely fatal.